The Center of Our Galaxy

On ….. clear, moonless night ….. shimmering light of ….. Milky Way glows especially bright toward ….. constellation Sagittarius. For years ….. astronomers have been aware, from ….. distribution of ….. groups of ….. stars and from ….. measurements of ….. stellar motions, that objects in our galaxy must travel in orbits around ….. center located in that direction. ….. astronomers also have found that in most cases other galaxies are especially bright toward ….. center because ….. density of ….. stars increases markedly there. In many instances ….. central regions also seem to be ….. sites of intriguing behavior, including ….. generation of enormous quantities of ….. energy, peculiar radiations and other unusual effects. More and more, it seems that ….. massive, unimaginably dense objects - ….. black holes - lie at ….. heart of some of these galaxies. Could our own galaxy also harbor such ….. exotic object at its center?

….. central region of ….. Milky Way has fascinated ….. astronomers for many decades. After all, our galactic center is only about 25,000 light-years away as opposed to …. millions of ….. light-years for ….. centers of ….. nearest other galaxies, and so it is ….. one astronomers might reasonably hope to see and to understand best. Yet for ….. long time there was no direct way to see ….. center of our galaxy or to learn much about it, because it is cloaked in ….. large and dense clouds of ….. gas and ….. dust.

….. recent discoveries and new technologies have made it possible at last to study ….. center of our own galaxy in some detail. These developments include ….. improved techniques for collecting and analyzing ….. astronomical radio wavesand infrared radiation as well as ….. space flights above ….. earth's atmosphere, which have made possible ….. detecting of ….. energetic X-ray and gamma-ray radiation emanating from ….. center of ….. galaxy.

All these types of waves - radio, infrared, X-ray and gamma-ray - are similar to ….. visible light in that they are all forms of electromagnetic radiation and differ only in their wavelengths and energy levels. Unlike ….. light, however, they can penetrate ….. interstellar clouds of dust with some ease and hence provides ….. window into ….. structure and dynamics of ….. galactic center.

from 'What is Happening at the Center of Our Galaxy?' by Charles H Townes & Reinhard Genzel, © 1990 by Scientific American, Inc. All rights reserved. (AmE)